%0 Generic %1 liu2013extinction %A Liu, Guilin %A Calzetti, Daniela %A Hong, Sungryong %A Whitmore, Bradley %A Chandar, Rupali %A O'Connell, Robert W. %A Blair, William P. %A Cohen, Seth H. %A Frogel, Jay A. %A Kim, Hwihyun %D 2013 %K dust extinction geometry hii %T Extinction and Dust Geometry in M83 HII Regions: An HST/WFC3 Study %U http://arxiv.org/abs/1311.0871 %X We present HST/WFC3 narrow-band imaging of the starburst galaxy M83 targeting the hydrogen recombination lines (H$\beta$, H$\alpha$ and Pa$\beta$), which we use to investigate the dust extinction in the HII regions. We derive extinction maps with 6 parsec spatial resolution from two combinations of hydrogen lines (H$\alpha$/H$\beta$ and H$\alpha$/Pa$\beta$), and show that the longer wavelengths probe larger optical depths, with $A_V$ values larger by $\gtrsim$1 mag than those derived from the shorter wavelengths. This difference leads to a factor $\gtrsim$2 discrepancy in the extinction-corrected H$\alpha$ luminosity, a significant effect when studying extragalactic HII regions. By comparing these observations to a series of simple models, we conclude that a large diversity of absorber/emitter geometric configurations can account for the data, implying a more complex physical structure than the classical foreground "dust screen" assumption. However, most data points are bracketed by the foreground screen and a model where dust and emitters are uniformly mixed. When averaged over large ($\gtrsim$100--200 pc) scales, the extinction becomes consistent with a "dust screen", suggesting that other geometries tend to be restricted to more local scales. Moreover, the extinction in any region can be described by a combination of the foreground screen and the uniform mixture model with weights of 1/3 and 2/3 in the center ($łesssim$2 kpc), respectively, and 2/3 and 1/3 for the rest of the disk. This simple prescription significantly improves the accuracy of the dust extinction corrections and can be especially useful for pixel-based analyses of galaxies similar to M83.

@misc{liu2013extinction, abstract = {We present HST/WFC3 narrow-band imaging of the starburst galaxy M83 targeting the hydrogen recombination lines (H$\beta$, H$\alpha$ and Pa$\beta$), which we use to investigate the dust extinction in the HII regions. We derive extinction maps with 6 parsec spatial resolution from two combinations of hydrogen lines (H$\alpha$/H$\beta$ and H$\alpha$/Pa$\beta$), and show that the longer wavelengths probe larger optical depths, with $A_V$ values larger by $\gtrsim$1 mag than those derived from the shorter wavelengths. This difference leads to a factor $\gtrsim$2 discrepancy in the extinction-corrected H$\alpha$ luminosity, a significant effect when studying extragalactic HII regions. By comparing these observations to a series of simple models, we conclude that a large diversity of absorber/emitter geometric configurations can account for the data, implying a more complex physical structure than the classical foreground "dust screen" assumption. However, most data points are bracketed by the foreground screen and a model where dust and emitters are uniformly mixed. When averaged over large ($\gtrsim$100--200 pc) scales, the extinction becomes consistent with a "dust screen", suggesting that other geometries tend to be restricted to more local scales. Moreover, the extinction in any region can be described by a combination of the foreground screen and the uniform mixture model with weights of 1/3 and 2/3 in the center ($\lesssim$2 kpc), respectively, and 2/3 and 1/3 for the rest of the disk. This simple prescription significantly improves the accuracy of the dust extinction corrections and can be especially useful for pixel-based analyses of galaxies similar to M83.}, added-at = {2013-11-06T15:03:42.000+0100}, author = {Liu, Guilin and Calzetti, Daniela and Hong, Sungryong and Whitmore, Bradley and Chandar, Rupali and O'Connell, Robert W. and Blair, William P. and Cohen, Seth H. and Frogel, Jay A. and Kim, Hwihyun}, biburl = {https://www.bibsonomy.org/bibtex/20e4b21e10504d78a1fd31e0cb8864aa2/miki}, description = {[1311.0871] Extinction and Dust Geometry in M83 HII Regions: An HST/WFC3 Study}, interhash = {56f6bbe13fb97a09186b29e4514d8572}, intrahash = {0e4b21e10504d78a1fd31e0cb8864aa2}, keywords = {dust extinction geometry hii}, note = {cite arxiv:1311.0871Comment: 7 pages, 4 figures, 1 table. Accepted for publication in ApJ Letters}, timestamp = {2013-11-06T15:03:42.000+0100}, title = {Extinction and Dust Geometry in M83 HII Regions: An HST/WFC3 Study}, url = {http://arxiv.org/abs/1311.0871}, year = 2013 }